By Ron Cowen
Every 11 years, the sun reaches a peak in its turbulent activity, sporting huge numbers of sunspots and hurling many billion-ton clouds of charged particles into space. At about the same time, the sun’s magnetic poles flip: North becomes south, and south becomes north (SN: 3/3/01, p. 139: Available to subscribers at Magnetic flip heralds solar max).
Solar physicists have had scant clues about why this switch happens, but a new study suggests that the clouds, known as coronal mass ejections (CMEs), play a central role. By prying loose magnetic-field loops anchored to the visible solar surface, coronal mass ejections may sweep the surface clean of old magnetic fields and prepare the sun for its magnetic reversal.